The present invention relates to a circuit component mounting device in which a circuit component is mounted on a substrate, and particularly relates to a structure of a circuit component mounting device in which conductor members provided on a substrate adhere to a circuit component by means of a solder.
Recently, circuit component mounting devices are being developed in which a highly-integrated circuit component is mounted and the mainstream structure thereof employs a circuit component covered with an insulative sealing resin in view of cost merits such as efficient production and the like. The circuit component is mounted on a set substrate after being packaged using a solder as an adhesive. This solder is dissolved in reflow for mounting to involve solder bridging that brings a short circuit between electrodes of the circuit component. This phenomenon is such that a several-micron gap remaining between the circuit component and the surface of the substrate is too small to be filled with the sealing resin sufficiently and the solder dissolved in mounting of a circuit component mounting device to the set substrate runs through the gap by pressure by its volume expansion, causing a short circuit between the electrodes. FIG. 7A is a section showing a structure of a conventional circuit component mounting device. As shown in FIG. 7A, the conventional circuit component mounting device includes: a resin substrate 101; vias 106 of which via holes passing through the resin substrate 101 are filled with a conductive resin; electrodes 105 that cover parts of the principal face of the resin substrate 101 where the vias 106 are exposed; a circuit component 103 provided on the electrodes 105 and composed of a main body 103a and electrode portions 103b; a solder 104 for allowing the electrodes 105 and the circuit component 103 to adhere to each other; an insulative sealing resin 102 that covers the circuit component 103 and the solder 104; and electrodes 111 that cover parts of the reverse face of the resin substrate 101 where the vias 106 are expose.
FIG. 7B is a section showing in detail a structure of the electrodes 105 of the conventional circuit component mounting device. As shown in FIG. 7B, each conventional electrode 105 is composed of: a Cu layer 121 covering the top of the via 106 (shown in FIG. 7A) and having a thickness of 10 to 40 μm; a Ni layer 122 provided on the Cu layer 121 and having a thickness of 6 μm; and an Au layer 123 provided on the Ni layer 122 and having a thickness of 0.5 μm.
In the above structure, the two electrode portions 103b provided on the sides of the main body 103a of the circuit component 103 are mounted on the two electrodes 105 provided on the principal face of the resin substrate 101. A space 107 is created in a region below the main body 103a of the circuit component 103, that is, a region between the two electrodes 105. The solder 104, which allows the electrode portions 103b and the electrodes 105 to adhere to each other, is liable to enter into the space 107.
Referring to countermeasures to prevent the solder bridging, there is a method in which the flow of the solder is inhibited by enlarging the space 107 between the circuit component 103 and the resin substrate 101 and filling the insulative sealing resin 102 therein. As one kind of this method, there has been proposed a method in which a solder resist (not shown) having height to some extent is provided on each side of the space 107 so as to support the circuit component 103 and the sealing resin is allowed to flow into the space 107 increased in height (see Japanese Patent Application Laid Open Publication No. 2004-103998A).
In association with size reduction of the circuit component mounting devices, the circuit components reduce its size, also. For example, in a circuit component 103 in 0.6 mm×0.3 mm size, the distance between the electrodes is about 0.25 mm. In general, according to the design rule for the solder resist, the minimum width and the maximum adjacent distance are about 0.1 mm, and therefore, it is difficult to provide a solder resist having sufficient thickness on each side of the space 107 in the case where the width of the space 107 between the electrodes 105 is 0.25 mm. Under the circumstances, it is necessary to form the space 107 in sufficiently large size even in a case using such a small-sized circuit component 103.
Further, in association with the size reduction of the circuit component mounting devices, the circuit components 103 to be mounted on the devices are highly integrated. This invites electromagnetic field interference between the circuit component 103 and a circuit pattern (not shown) both of which are provided on the resin substrate 101, degrading electric characteristics of the devices. For preventing this incident, a wall serving as a shield may be provided between the circuit component 103 and the circuit pattern. However, this inhibits higher integration.